Mr Robot - Elliot.java

import java.util.*;
import java.io.*;

class Main {
    static class FastReader {
        BufferedReader br;
        StringTokenizer st;

        public FastReader() {
            br = new BufferedReader(new InputStreamReader(System.in));
        }

        String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        long nextLong() {
            return Long.parseLong(next());
        }

        double nextDouble() {
            return Double.parseDouble(next());
        }

        String nextLine() {
            String str = "";
            try {
                str = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }
    }

    public static String call(String m, String str) {

        // System.out.println(n+" "+str);

        int n = Integer.parseInt(m);

        StringBuffer left = new StringBuffer("");
        StringBuffer right = new StringBuffer("");

        if (str.length() <= 2) {
            return str;

        }

        int mid = (n - 1) / 2;

        for (int j = 0; j < mid; j++) {

            left.append(str.charAt(j));

        }
        for (int k = (mid + 1); k < n; k++) {

            right.append(str.charAt(k));

        }

        StringBuffer ans = new StringBuffer("");

        ans.append(str.charAt(mid));

        ans.append(call(Integer.toString(left.length()), left.toString()));
        ans.append(call(Integer.toString(right.length()), right.toString()));

        return ans.toString();

    }

    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);

        int tc = sc.nextInt();
        sc.nextLine();
        for (int i = 0; i < tc; i++) {
            String n = sc.nextLine();
            String str = sc.nextLine();
            System.out.println(call(n, str));
        }
    }
}